Drafting instrument



Dec. 3, 1929.

F. EL MEYER.

DRAFTING INSTRUMENT Filed Aug. 30, 1929 MWWWWN INVENTOR flour/ls E Me er. M M

ATTORNEY Patented Dec. 3, 1929 UNITEDSTATES PATENT OFFICE,

. runners n. MEYER, or PHILADELPHIA, rnnns'rnvnnm, nssrenon T THEO. AL'IEN- nnnn & sons, or PHILADELPHIA, rnnnsynvnmn, A eonronnrron or rnnnsrn VANIA DRAF'IING INSTRUMENT Application filed August 30, 1929.. Serial No. 389,347.

This invention relates to drafting instruments and more particularly to instruments such as bow compasses or dividers.

Such instruments comprise a pair oflegs susceptible to relatively spaced adjustment, one leg carrying a needlepoint to form an axis, the other leg carrying a lead or a pen to described an are about the axis. When the legs arerelatively widely spaced apart small differences in their respective efiective lengths make but little diderence in the successful use of the instrument. When, however, the legs are set close together for describing small arcs, then small differences in the respective lengths of the legs assume tremendous proportions and it is impossible tosuccessfully operate the instrument until the effective lengths of the respective legs has been equalized. Such differences in length occur,among other reasons, because of wear on the lead. Assuch devices have been constructed in the past, howeventhe only adjustment provided, whether by providing an axially slidable needle point, or a threaded rotatable needle point, could not be availed of without first eparating the legs to enable the operator to grasp the parts for adjustment. Inasmuchas the adj ustment of the length of the axis leg by moving the needle point must be done by sighting the tip of the needle point to line it up with the tip of the lead or pen, it will be clear that the previous adjustable constructions failed at the time when they were most needed, asthe proper sighting must and can only be done with the legs inclose adjacency. Furthermore, as such devices have been provided hitherto, the necessary adjustment was accomplished by grasping the end of the needle point itself, which action obviously precluded a,sight during the actual adjustment, thus further militating against the efiiciency of the instrument. Moreover, it has been the practice to grind or bevel on one side of the needle point to bring a flat side of the needle in close proximity to the flat side of the beveled lead. Previous practices have precluded the maintenance of the properly juxtaposed positions of the fiat sides, owing to incidental rotation of the needle point in using either of the earlier modes of adjustment.

Among the objects of this invention are to provide a leg of the drawing instrument with an adjustable needle point which is quick, certain and accurate in its adjustment; to provide a drawing instrument with an adjustable needle point wherein the adjusting means are accessible to both hands of the operator without disturbing the arcuate setting of the instrument; to provide means for accurately and easily adjusting the needle point of a bowcompass when both legs are close together; to provide in a drawing instrument an adjustable needle point which is non-rotatable relative its associated leg; to provide a leg of a drawing instrument with a needle point extension having a blunt end and which needle point is susceptible to reversing for the safe carrying of the instrument; to provide a drawing instrument with an adjustable needle point, which is arranged for fine and accurate adjustments without obscuring the operators full and clear vision of the tip of the needle point during such adjustments; to provide an adjustable needle point on an instrument which is always visible to the operator regardless of the action oi adjusting the use dle point; to provide a drawing instrument with an extensible needle point which is rigid and firm in use; to provide a bow-compass with a reversible removable needle point; to improve generally drawing instruments of the bow-compass type; and many other objects and advantages as will become. more apparentas the description proceeds.

The invention, herein, is applicable to many types of drawing instruments, whether compasses, dividers, or the like, but will be described for purely illustrative purposes in connection with its application to bow-compasses, whether pencils or pens, as used for drawing relatively small circles or arcs thereof.

111 the accompanying drawings:

Fig. 1, represents a plan of an assembled instrument according to the invention,

Fig. 2, represents a fragmentary side elevation of the axis leg showing the needle point in one adjusted position, and I Fig. 3, represents a fragmentary plan VlGW of the operators hands holding the instrui which may be'beveled off slightly as shown ment and in the act'of adjusting the needle point, and disclosing the unobstructed sight of the tip of the needle point, with the instrument disclosed with the legs in closely adjusted relative position. I

Such aboW-pencil is disclosed in the draw ings and comprises a handle, head, or finger piece 10, connected to the apex of the spring legs 11 and 12. Leg 11 comprises the ruling leg and carries a lead 13 vertically adjustable in a barrel 14 clamped upon the lead 13 by means of a set screw 15. It will be understood that in place of the lead and lead holding part, there may be provided a pen which for all of the purposes of this invention are full equivalent. It is usual to bevel one side of'the lead as'at 16, to form a thin lining edge 17 for contact with the paper. Leg 12 comprises the axis leg with relation to which the 'legll is rotated to describean arcuate path.

' The invention herein, is particularly relevant j to the axis leg.

' The axis leg 12 comprises at itsupper portion athin resilient shank tending to urge leg 12 away from the longitudinal median axis of the instrument (as does leg 11 i i the opposite direction). Just below the resilient shanks of the legs, each leg is enlarged to receive the transverse adjusting belt or screw 18, having the knurled head 20 by which it may be rotated and the legs caused to be drawn together againstthe resilience of the spring portions thereof. 7 This portion of the invention may be of conventional construction and will not be described in detail.

Leg 12 provides a flat face 21 on the inside of the leg. The outer face may be of any desired configuration. At its lower end the leg is formed in a tubular barrel, or sleeve, or the like, as at 22, the passage or opening 23 of which is formed substantially parallel to the fiat face 21. The upper portion 24:, of

. the barrel 'or sleeve, forms a shoulder, sub- I and threaded'as. at 25 to receive a clamping stantially perpendicular to the flat face 21. e outer portion of the barrel 22 is drilled screw 26, extending transversely of the leg i 12,with the knurled head 27 thereof disposed in such position as to be readily grasped by the thumb and fore-finger of the operators left hand, and with the end of the screw extending into the opening 23.

It will be understood that the lower portion of the leg 12, hearing the flat face 21 preferablywill be of substantially uniform thickness or width. I r j A needle point is provided comprising the shank 28 of suchdiameter as to be slidably received in theopening 23, having a point 30 'i each other and to the flat face 21 of the leg.

The lateral edges of the head may be ridged or knurled as shown at 32. It will be understood that the preferred form of the needle point head is one in which both lateral edges are knurled, and in which the head is of a lateral Width slightly greater than the thickness of the adjacent leg as to extend a little beyond at least one side edge thereof when in'position. To this end the needle point is inserted axially into the opening in the barrel or sleeve (with the clamping screw 26 retracted to permit the insertion), with one flat face of the head 31 in sliding contact with the flat face 21 of the leg. It will be understood that the knurled edge of the head 31 of the needle point will be elevated slightly above the edge of the leg in such manner that the right hand thumb 33 of the operator may rest on the raised portion and slide the needle point longitudinally of the barrel to vary the effective length of the axis leg, the instrument being supported by the right hand forcfinger 34' as S1OWI1. It is of importance to note that the longitudinal movement of the needle point is for its full length, and is limited only by the contact of the enlarged head 31 with the shoulder 24 of the barrel in one direction, and by the length of the barrel in the other. It will be clear that it is not necessary that both edges of the flattened head 31 of the needle point be extended laterally beyond the adjacent edge of the leg, as such extension on one side is quite adequate, and, in'the fine adjustments to be made when the legs are close together but one side of the head is utilized. It will be understood that in order to facilitate the adjustment of the device the upper side of the leg 11 in the vicinity of the pencil clamp, or pen, will be as smooth as possible and preferably with its upper surfaces in substantial registry with the upper surface of the leg 12, below the level of the projecting edge of the head 31 of the needle point, so that the edge of the needle point head is the highest point, to facilitate frictional contact with the thumb of the operator. Moreover, it will be understood that the normal disposition of the needle point is such that there is a more or less appreciable longitudinal space between the said head and the head 27 of the set screw 26, to give clearance for the fingers of the operator. With the instrument grasped in the right hand of the operator as shown in Fig. 3, the thumb 35 and fore-finger 36, of the left hand of the operator are free to grasp and operate the knurled head 27 of the clamping screw, as will be obvious.

In the operation of the instrument wear inevitably occurs on the tip of the lead of the bow-compass, which, as noted, is of no particular moment when describing large arcs. When, however, arcs of minute radii are to be described, such wear, or other factors resulting in variations in the efiective lengths jof the respective legs, (such as removal and lreplacement of the sharpened lead, or the like) assumes such proportions as to preclude the operation of the instrument until the legs have been rendered substantially equal in length. In order to determine the relative lengths of the legs it is properly customary to sight both legs against a light background when they are as close together as possible, and then remedy the deficiency that may exist. With the instant invention the operator may screw the legs so close together that they are in substantial contact, hold the instrument in the right hand to sight the tips of the legs against a contrasting background, seize and manipulate the set-screw 26, by its head 27, with the left hand, so as to retract same and release the needle point in the barrel, then, while thus supporting the instrument, permit the thumb of the right hand torest naturally upon the elevated portion of the head 31, and by appropriate sliding move ments adjust the needle point to the exact position desired, then while holding the needle point in proper position with the thumb, turn the set-screw with the left hand to lock the needle point against movement. All of this while the legs are in intimate juxtaposed position if necessary and without obscuring the operators vision of the tip of the needle point.

Another factor of importance in the invention which may be mentioned at this point is that when the instrument has a charged pen instead of a lead as the lining element, it is possible to adjust the needle point accurately and quickly while the compass is tightened so that the legs are as close as possible, withoutdanger of coming into contact with the ink and smearing the fingers and, of course, without obscuring the vision of the operator on the needle point tip.

it will be evident that owing to the sliding relation of the flat head 31 of the needle point to the flattened surface 21 of the leg, all rotative motion of the needle point is precluded and any predetermined relation of the tip of the needle point and the leg such as a beveled or otherwise eccentric tip, is maintained, despite the longitudinal adjustment.

Moreover, it will be understood that the flattened head 31 of the needle point provides a blunt end that may be disposed as the terminus of the leg, for safely carrying the instrument with the needle point reversed, and with the needle point tip protected by the thicker portion of the leg above'the barrel.

The simplicity, economy, and efliciency of the invention are deemed to be obvious, as is the fact that various modifications of the invention may occur to those skilled in the art, and such are to be construed as within the scope of the invention, unless otherwise limited in the appended claims.

I claim as my invention:

1. I11 a drawing instrument, a needle point arranged for operative adjustable association with the axis leg thereof, comprising a cylindrical shank, a pointed tip, and an enlarged flattened head, the head being of a thickness substantially the same as the diameter of the shank and having a pair of substantially parallel faces extending parallel to the shank, the edges of which are joined by serrated surfaces, symmetrically spaced from the shank.

2. In a drawing instrument, an axis leg comprising a shank and an offset barrel having a bore parallel with the inner plane face of the shank, a needle point including a shank slidable in the bore of the barrel, and having a head of greater width than the inside of the axi leg, and including a flattened face slidably engaging the said face of the leg when the shank is within the bore, one side of the head extending beyond the edge of the leg in position to be engaged by the thumb of the operator.

3. In a drawing instrument, an axis leg having a barrel, said leg being cut away above the barrel to provide a flattened guiding face, a needle point including a shank and an enlarged head, the head including a flattened face extending laterally in each direction beyond the shank and terminating at one side in thumb-engaging surface, said barrel having a bore substantially tangential with the flattened guiding face, said needle point being arranged for sliding engagement in the barrel with the flattened face in sliding engagement with the flattened guiding face of the leg and with the thumb-engaging surface disposed above the top face of said leg for direct engagement by the operator.

4. A drawing instrument comprising two relatively adjustable legs arranged for close association with the operative ends of the legs in close proximity, one leg comprising an axis leg and having a longitudinally eX- tending tubular barrel inwardly offset toward the other leg, the legs having a clearance above the barrel when in proximity, a needle point slidable in the barrel and having a head of such lateral thinness as to be received in the clearance between the legs and of such width as to extend slightly above the level of the adjacent legs to form a thumb piece, said head having a surface sliding on its leg to guide the head, and means independent of the thumb piece for locking the needle point in position on the axis leg.

Signed at Philadelphia, county of Philadelphia, and State of Pennsylvania, this 28 day of Aug, 1929.

FRANCIS E. MEYER.

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